U.S. patent application number 10/427505 was filed with the patent office on 2004-03-04 for vehicle bumper assemblies and associated towing assemblies.
This patent application is currently assigned to WAGON AUTOMOTIVE (UK) LIMITED. Invention is credited to Edwards, Richard John, Harrison, Tom Copeman.
Application Number | 20040041416 10/427505 |
Document ID | / |
Family ID | 9936474 |
Filed Date | 2004-03-04 |
United States Patent
Application |
20040041416 |
Kind Code |
A1 |
Harrison, Tom Copeman ; et
al. |
March 4, 2004 |
Vehicle bumper assemblies and associated towing assemblies
Abstract
A tow nut for a vehicle bumper assembly having an engagement
portion by which a tow eye may be connected thereto and an
attachment portion by which the tow nut may be attached to the
assembly, characterized in that the tow nut is provided, between
the engagement and attachment portions, with a zone of weakness
whereby relative movement between the engagement portion and the
assembly is permitted, under an impact condition.
Inventors: |
Harrison, Tom Copeman;
(Suffolk, GB) ; Edwards, Richard John;
(Staffordshire, GB) |
Correspondence
Address: |
BAKER BOTTS L.L.P.
30 Rockefeller Plaza
New York
NY
10012-4498
US
|
Assignee: |
WAGON AUTOMOTIVE (UK)
LIMITED
|
Family ID: |
9936474 |
Appl. No.: |
10/427505 |
Filed: |
May 1, 2003 |
Current U.S.
Class: |
293/117 |
Current CPC
Class: |
B60D 1/488 20130101;
B60D 1/485 20130101; B60D 1/565 20130101; B60D 1/52 20130101 |
Class at
Publication: |
293/117 |
International
Class: |
B60R 019/48 |
Foreign Application Data
Date |
Code |
Application Number |
May 11, 2002 |
GB |
GB 0210801.7 |
Claims
We claim:
1. A tow nut for a vehicle bumper assembly having an engagement
portion by which a tow eye may be connected thereto and an
attachment portion by which the tow nut may be attached to the
assembly, characterized in that the tow nut is provided, between
the engagement and attachment portions, with a zone of weakness
whereby relative movement between the engagement portion and the
assembly is permitted, under an impact condition.
2. A tow nut according to claim 1 wherein the zone of weakness is
associated with a reduced thickness portion of the tow nut.
3. A tow nut according to claim 1 having a frangible portion at or
near the zone of weakness.
4. A tow nut according to claim 2 wherein the attachment portion
comprises part of a flange and wherein the reduced thickness
portion is associated therewith.
5. A tow nut according to claim 4 wherein the reduced thickness
portion is provided by an undercut in the flange.
6. A tow nut according to claim 2 wherein the reduced thickness
portion extends about a principal axis of the engagement
portion.
7. A tow gut according to claim 2 wherein the reduced thickness
portion is generally part-cylindrical.
8. A tow nut according to claim 2 wherein the engagement portion is
generally tubular and wherein the reduced thickness portion is
radially spaced from the engagement portion.
9. A tow nut according to claim 8 wherein the reduced thickness
portion is radially spaced from an outer wall of the engagement
portion.
10. A tow nut according to claim 5 wherein the undercut has a depth
of at least half of the flange depth.
11. A tow nut according to claim 10 wherein the undercut depth is
about 80% of the flange depth.
12. A tow nut according to claim 2 wherein the reduced thickness
portion is about 1 mm thick.
13. A towing assembly for use with a vehicle bumper assembly, the
towing assembly comprising an engagement formation by which the
assembly may be connected to a towing vehicle and an attachment
formation by which the towing assembly is attached to the bumper
assembly, the towing assembly being provided, between the
engagement formation and the attachment formation, with a zone of
weakness whereby relative movement between the engagement formation
and the bumper assembly is permitted, under an impact condition.
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates, in broad terms, to the field of
vehicular (principally automotive) crash systems and relates, in
particular, to vehicular bumper assemblies that are provided with a
forwardly-disposed towing facility whereby a vehicle may be towed
by another.
[0002] A number of important considerations must be borne in mind
during the design and production of such bumper assemblies. First
and foremost, the impact-absorbing function of the bumper must be
carefully monitored, so as to ensure that as much impact energy as
possible is absorbed by the bumper assembly, and thus not
transmitted to the main vehicle structure, or to the occupants
thereof.
[0003] To this end, bumper assemblies typically comprise a metallic
(sometimes rolled) front beam which may be attached, towards a rear
part thereof, to a crash box, which is typically designed to deform
("crumple") under an impact condition. Alternatives to crash box
systems are also known, in which the front beam is attached
directly to a vehicle chassis rail, with the rail sometimes being
provided with a sacrificial element to perform the energy-absorbing
function. In both cases, however, the front face of the metallic
beam is usually provided, for cosmetic reasons, with a covering, or
skin, although such components contribute little to the
impact-absorbing characteristics of the overall bumper
assembly.
[0004] It has also become common practice, particularly in the
domestic and light commercial vehicle industries, to provide, in
conjunction with a front bumper assembly, some means whereby the
vehicle concerned can be towed by another vehicle, in the case of
breakdown, accident damage, insufficient fuel and the like.
[0005] To provide this capability, a so-called "tow nut" is
attached to or provided with the forwardly-disposed bumper beam,
with the tow nut having an internal thread to receive an externally
threaded "tow eye" or "tow hook" having a circular or hooked end,
by which a rope or other such line may be used to connect the towed
and towing vehicles together. The term "tow nut" should thus be
interpreted broadly, by reference to the function that it performs:
it need not, of course, be "nut" shaped.
[0006] However, problems have arisen with currently available
towing assemblies, principally as the rigid nature of the tow nut
and its securement to the forwardly-disposed bumper beam seriously
hinders the ability of the beam to crumple under impact conditions.
In addition, as it has become the norm to provide a single tow nut
towards one end of the forward bumper beam (and thus to one side of
the front of the vehicle), the strength and hence impact-absorbing
characteristics of the beam vary considerably along its length. As
will be understood, this means that a vehicle provided with such a
bumper assembly will suffer different types and amounts of damage
during a collision, depending on which part of the vehicle is
struck.
[0007] It is an object of the present invention to provide an
improved tow nut that overcomes or at least reduces these problems.
Other objects of the invention are to provide improved towing and
vehicle bumper assemblies.
SUMMARY OF THE INVENTION
[0008] In accordance with a first aspect of the present invention,
there is provided a tow nut for a vehicle bumper assembly having an
engagement portion by which a tow eye may be connected thereto and
an attachment portion by which the tow nut may be attached to the
assembly, characterized in that the tow nut is provided, between
the engagement and attachment portions, with a zone of weakness
whereby relative movement between the engagement portion and the
assembly is permitted, under an impact condition.
[0009] The zone of weakness may be associated with a reduced
thickness portion in the tow nut.
[0010] The tow nut preferably is provided with frangible portion at
or near the zone of weakness.
[0011] The attachment portion may comprise part of a flange and the
reduced thickness portion may be associated therewith.
[0012] Preferably, the reduced thickness portion is provided by any
undercut in the flange.
[0013] The reduced thickness portion may extend about the principal
axis of the engagement portion.
[0014] The reduced thickness portion may be generally
part-cylindrical.
[0015] Preferably, the engagement portion is generally tubular,
with the reduced thickness portion being radially spaced from a
wall into the tube.
[0016] Conveniently, the reduced thickness portion is radially
spaced from an outer wall of the tube.
[0017] Various depths of undercut maybe employed, and the depth of
the undercut may thus be at least half the depth of the flange.
[0018] Preferably, the depth of the undercut is about 80% of the
depth of the flange.
[0019] Conveniently, the reduced thickness portion is about 1 mm
thick.
[0020] In accordance with a second aspect of the present invention,
there is provided a towing assembly for use with a vehicle bumper
assembly, the towing assembly comprising an engagement formation by
which the assembly may be connected to a towing vehicle and an
attachment formation by which the towing assembly is attached to
the bumper assembly, the towing assembly being provided, between
the engagement formation and the attachment formation, with a zone
of weakness whereby relative movement between the engagement
formation and the bumper assembly is permitted, under an impact
condition.
[0021] The zone of weakness of the towing assembly may be
substantially in accordance with the first aspect of the present
invention.
[0022] In accordance with a third aspect of the present invention,
there is provided a vehicle bumper assembly having a tow nut
substantially in accordance with the first aspect of the present
invention.
[0023] In accordance with a fourth aspect of the present invention,
there is provided a vehicle bumper assembly having a towing
assembly substantially in accordance with the second aspect of the
present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] The invention, in its various aspects, will now be
described, in greater detail, but strictly by way of example only,
by reference to the accompanying drawings, of which:
[0025] FIG. 1 is a perspective view of a vehicle bumper assembly in
accordance with the present invention;
[0026] FIG. 2 is a schematic illustration, from above, of part of
the assembly of FIG. 1;
[0027] FIG. 3a is a close-up section of a tow nut in accordance
with the present invention;
[0028] FIG. 3b is an axial view, from above, of the tow nut of FIG.
3a;
[0029] FIG. 4 is a perspective, schematic, illustration of the
outer surfaces of the tow nut of FIGS. 3a and 3b, showing how the
nut is welded to a bumper mounting plate;
[0030] FIG. 5 is an axial view, from above, of the tow nut and
welds of FIG. 4;
[0031] FIGS. 6a, 6b and 6c illustrate, in schematic form, a number
of different configurations of recess that may be provided in the
tow nut shown in the preceding figures in accordance with the
present invention; and
[0032] FIGS. 7a and 7b illustrate still further possible
configurations of recess in accordance with the present
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0033] Referring to the Figures, a vehicle front bumper assembly 10
comprises a forwardly disposed bumper beam 11 which, in this
example, is formed by rolling medium to high strength steel sheet,
to form the elongate and partially hollow configuration shown.
Although not illustrated in the drawings, it will of course be
understood that, in practice, the beam 11 will usually be provided
with a cosmetic and somewhat protective outer skin which may be
formed from a rubber or plastics material, for example. The beam 11
is connected, via mounting plates 12, to crash boxes 13 which,
whilst also formed from a metallic material, are specifically
designed to collapse or "crumple", in the event that the vehicle
experiences an impact. The crash boxes 13 are connected, towards
their rear ends, to crash box back plates 14 which are fastened, in
generally conventional manner, to a rigid part of the vehicle
structure.
[0034] A generally circular aperture 15 is provided at one end 16
of the bumper beam 11, the aperture 15 serving to receive a tow nut
17 which, as shown in FIGS. 3a, 3b, 4, 5, 6a, 6b and 6c, has a
generally tubular engagement portion 18 which is provided, on its
internal surface, with a threaded configuration. The engagement
portion 18 is attached to or integral with, at a rear end 19
thereof, a generally circular flange 20 which abuts a
rearwardly-facing surface 21 of the mounting plate 12. The flange
may, of course, be of a different configuration. The
forwardly-disposed surface of the flange 20 constitutes an
attachment portion by which the tow nut 17 may be attached to the
mounting plate 12, and thus secured in relation to the rest of the
bumper assembly 10. As shown in FIGS. 4 and 5, the tow nut 17 is
preferably attached to the mounting plate 12 using four evenly
circumferentially-spaced welds 22, although other attachment
methods may, of course, also be used. An even, circumferential
distribution of weld points is advantageous as this ensures that
the tow nut 17 is able to withstand laterally-exerted forces such
as may be experienced when the tow nut 17 is used, during
transportation of a vehicle, to "tie down" the vehicle to restrict
movement thereof during transit. It will however be appreciated
that other weld configurations and arrangements could conceivably
be employed, and it may be desirable, in cases where extra strength
is required, to provide a single circumferentially-extending weld
about the attachment portion, to the mounting plate 12. As shown in
FIG. 1, the principal purpose of the tow nut 17 is to receive, on a
temporary basis, a tow eye 23 which, in generally conventional
manner, comprises an externally-threaded generally elongate shank
24 which, in use, is threadedly engageable with the
internally-threaded female tow nut 17. The shank 24 is attached to
or integral with an eye element 25 to which, in appropriate
circumstances, a rope or other such towing line may be attached, to
enable the vehicle to be towed.
[0035] As shown in FIGS. 3a, 3b, 6a, 6b and 6c, the tow nut 17 is
provided, on its underside 26, with a recessed channel 27 which
extends, when the tow nut 17 is viewed axially, in a generally
circular manner about the principal axis 28 of the tow nut 17. The
channel 27, which constitutes a continuous undercut in the flange
20, creates a similarly generally circular reduced thickness
portion 29 that is disposed between the engagement and attachment
portions of the tow nut 17. As shown in FIGS. 6a, 6b and 6c, for
example, the recess may have a number of differing cross-sections,
although, in each case, it will be noted that the apex 30 of the
cross-section is offset from the outer wall 31 of the engagement
portion 18. This is to ensure the provision of a shoulder part 32
of generally full-thickness material which, in use, will abut the
rearwardly-disposed surface 21 of the mounting plate 12. The
provision of such full-thickness material is important during a
towing operation, to ensure that the tow nut 17, on, being pulled
axially away from the mounting plate 12, is held securely in
position. Nonetheless, by selecting an appropriate material, the
applicants envisage that it may also be possible to locate the
channel directly beneath, or close to, the outer wall 31.
[0036] As explained above, an important consideration in automotive
bumper design is the extent to which the bumper assembly is able to
absorb impact forces which are exerted when the vehicle is in
collision with another vehicle, or static object, for example. Such
energy absorption is important to minimize damage to the main
vehicle structure, but principally to reduce the effect of the
impact force on the occupants of the vehicle.
[0037] To this end, it is desirable to design vehicle bumper
assemblies so that as much crash energy is absorbed by the front
end of the vehicle, as possible, with the brunt being taken by the
bumper beam 11 and crash box 13 of the assembly 10. In order for
the bumper beam 11 to be able to collapse in the event of an
impact, it is important that the components thereof are able to
move in a generally rearwardly direction and that the "crumpling"
capability of the crash box is not restricted. The provision of the
undercut recess 27 in the flange 20 provides this, capability, in
that, in the event of a generally axially-directed impact, the tow
nut 17 will fail, in shear, at a zone of weakness defined by the
reduced thickness portion 29, disposed just above the apex of the
recess 27. As will be understood, this allows the generally tubular
engagement portion to move, generally axially, in relation to the
mounting plate 12, and hence to the rest of the bumper assembly 10,
which in turn allows the bumper beam 11 to collapse, in a somewhat
similar direction, towards the crash box 13. The positioning and
configuration of the recess 27 may be adjusted to "tune" the tow
nut 17 to fail, in shear, at a variety of different axial forces,
with it typically being desired for a shear fail to occur when an
axial force of 30 to 40 kN (kilo Newtons) is applied. In practice,
the failure force will lie somewhere between, the force at which
deformation of the bumper beam 11 commences and the force required
to initiate collapse of the rearwardly disposed crash box 13. What
this means is that, in the event of a minor impact, that does not
cause the bumper beam 11 to deform, the tow nut 17 will remain
intact and firmly secured to the mounting plate 12. However, where
a greater impact is experienced, the tow nut 17 may fail, in shear,
with the tubular body of the engagement portion 18 thus being
propelled generally rearwardly of the assembly, into the body of
the crash box 13. As the tubular body 18 has now become detached
from the mounting plate 12, it can simply fall towards the rear of
the crash box 13, thus ensuring that the crash box is able to
crumple largely unhindered.
[0038] To ensure that the tow nut 17 does not accidentally become
detached, in its entirety, from the mounting plate 12, it will be
understood that the weld strength will normally need to exceed the
strength of the zone of weakness defined by the undercut recess 27.
This can of course be achieved in a number of ways, although the
applicants have found that the total contact area between the welds
22 and the surface 21 of the plate 12 should exceed the upper
surface area of the generally disc-shaped zone of weakness.
[0039] As will be understood from the foregoing, the invention, in
its various aspects, provides a number of improvements in the field
of automotive bumper design, principally as the facility of the tow
nut to fail at a specified point, and under a known axial force,
enables the forwardly-disposed bumper beam to collapse in the event
of an impact, which, in turn, allows the energy absorbing aspect of
the assembly to function in an unhindered manner. The offset nature
of the undercut recess, however, ensures that the tow nut is
sufficiently resilient, when exposed to a towing force, thus
ensuring that it does not become separated inadvertently from the
mounting plate 12 when a towing operation is underway, or when the
associated vehicle is tied down, during transit.
[0040] As shown in FIGS. 7a and 7b, the undercut recess in the
flange 20 of the tow nut 17 may alternatively comprise a somewhat
disc-shaped cut-out 40. As shown in the drawings, the provision of
a reduced thickness (and hence reduced strength) zone is unaffected
by the alternative recess configuration, with it conceivably being
desirable to produce the tow nut in this way in an effort to reduce
material usage and hence manufacturing costs.
[0041] It should also be understood that, whilst in the examples,
the tow nut 17 is shown attached to the mounting plate 12 by
abutment of the flange 20 with a rearwardly-facing surface 21 of
the plate, it is envisaged by the applicants that the flange 20
could in fact be attached to the plate 12 by abutment with its
opposite (forwardly-facing) surface. Thus, by reference to FIG. 3a,
for example, it should be understood that, in use, the mounting
plate 12 may in fact be disposed in abutment with the underside 26
of the tow nut 17.
[0042] The features disclosed in the foregoing description, or the
following claims, or the accompanying drawings, expressed in their
specific forms or in terms of a means for performing the disclosed
function, or a method or process for attaining the disclosed
result, as, appropriate, may, separately, or in any combination of
such, features, be utilized for realizing the invention in diverse
forms thereof.
* * * * *